Silly question about Yanmar 315 mixing elbow

[kerrye]

I'm obviously missing something here. So in this system no seawater would discharge out the back of the boat with the exhaust?

[Pitou]

I'm obviously missing something here. So in this system no seawater would discharge out the back of the boat with the exhaust?

Yes the sea water exits out the back of the boat through the exhaust system.

The pressure of the exhaust gasses push the seawater flow from the shower head mixing elbow down the exhaust hose through the muffler and out the back of the boat. Gravity from proper pitch helps too. The seawater not only cools the freshwater side of your engine, air intake and heat exchangers it cools your exhaust gasses and it's components. These are the basics.

Check out the Seaboard link and start with the first article. Lots of drawings and pictures to walk you through.

[kerrye]

That's what I thought which is why I am still puzzled by the earlier post which said there was only exhaust coming out and no water.

[catalina_mike]

That's what I thought which is why I am still puzzled by the earlier post which said there was only exhaust coming out and no water.

The leak could be between the flange and salt water injection point. Withoue seeing it we are all guessing a bit. But the OP was no water just exhaust. This is possible as described.

[Pitou]

That's what I thought which is why I am still puzzled by the earlier post which said there was only exhaust coming out and no water.

The mixing elbow has a dry end connected to the turbo / engine side and a wet end connected to the black rubber exhaust hose. As Mike just described and Lee first suggested, we are surmising that there is an exhaust leak at the dry end at the flange with the turbo.

The best thing that you can do to understand this is to educate yourself and join boatdiesel.com for $25 and read the articles on marine exhausts as well as reading up at the Seaboard Marine site referenced above. Both of these sites will help you understand what is under your deck and how things work.

Here is an excerpt from Boat diesel that should help in your understanding of what I had posted previously to help you understand the OP's circumstance:

"Even on the factory "wet elbows" supplied by all of the manufacturers that I've seen, these two sections exist, though many people don't realize it. The inner pipe of this "wet elbow" is actually a 90-degree dry bend, or section, surrounded by raw water to keep the surface cool. At the end of this "wet" elbow, where the exhaust hose attaches, is where the water is introduced (hence the term "mixing elbow") and the exhaust NOW becomes wet. Inside this elbow is a smaller diameter (typically around 2 ½ - 5" ID) which is the dry side, and where the hose attaches, it expands to (or is surrounded by) 4-8" tubing/OD piping, depending on the engine size, etc..."

[kerrye]

I understand all that, and I'm not ignorant on marine exhaust sytems, but I took him to be saying that no water was coming out of the exhaust at the back of the boat which is what inspired the question about where it was going. If there was no water coming out of the exhaust at the back of the boat and no water into the bilge, there is something wrong with the cooling system other than a failed elbow. If there was water coming out at the back of the boat, the question about the bilge doesn't make sense.

[Jeremyvmd]

I think what he's saying is there was only exhaust coming from the LEAK not talking about the exhaust exit. And since there was no water coming from the elbow his bilge was dry and since the bilge was dry he knew no water was comign from the elbow...

[kerrye]

The answer to that question is easily determined by looking at the back of the boat so I assumed the question was about no water at the exhaust at the back of the boat.